[RFC] ATA host-protected area (HPA) device mapper?

[Jeff Garzik]

As I just mentioned on linux-ide in another email:
libata should -- like drivers/ide -- call the ATA "set max" command to 
fully address the hard drive, including the special "host-protected 
area" (HPA).  We should do this because the Linux standard is to export 
the raw hardware directly, making 100% of the hardware capability 
available to the user (and, in this case, Linux-based BIOS and recovery 
tools).

However, there are rare bug reports and general paranoia related to 
presenting 100% of the ATA hard drive "native" space, rather than the 
possibly-smaller space that the BIOS chose to present to the user.

My thinking is that [someone] should create an optional, ATA-specific 
device mapper module.  This module would layer on top of an ATA block 
device, and present two block devices:  the BIOS-presented space, and 
the HPA.

Such a module would make it trivial for users to ensure that partition 
tables and RAID metadata formats know what the BIOS (rather than 
underlying hard drive) considers to be end-of-disk.

Comments?  Questions?  Am I completely insane?  ;-)

	Jeff



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